Polymeric bodies of the type here considered include a core and a surrounding skin, the latter being usually denser than the former; thus, the polymeric core may be admixed with a foaming agent. The two constituents may be formed in separate molds though in many instances it is possible to produce them in a common mold cavity by successive injection steps.
When such a composite body is used in an environment containing sensitive electronic equipment, e.g. as pads or mats for the support of electrically operated office machines, the accumulation of static charges thereon must be prevented. For this purpose it is known in provide such bodies with an electronic shield or with inductive protection means; in particular, a metallic foil may be pasted onto an inner surface of the body or a thin layer of metallic powder may be sprayed upon that surface. Both procedures encumber the manufacturing process; the second one also entails the risk that some metal particles might land on the outer skin and mar its appearance or impair its continuity, thereby rendering the article unusable.